Coronary syndrome (for example, unstable angina, myocardial infarction, ischemic sudden death and the like) is caused by rupture of a coronary artery plaque (atheroma) followed by formation of a thrombus and the resultant occlusion of the lumen of a coronary artery. Peripheral artery occlusion is caused by rupture of an artery plaque (atheroma) followed by formation of a thrombus and the resultant occlusion of the lumen of a peripheral artery. These diseases are related closely to the characteristics of a plaque, and a lipid-rich plaque formed by accumulation of a macrophage retaining lipids such as cholesterol extensively onto the inner wall of a blood vessel is believed to cause coronary syndrome and peripheral artery occlusion. A lipid-rich plaque formed at carotid artery or intracerebral vessel is believed to cause cerebral apoplexy or cerebral infarction. Accordingly, regression and removal of a lipid-rich plaque are very important for preventing or treating coronary syndrome such as myocardial infarction and unstable angina as well as peripheral artery occlusion, cerebral apoplexy, or cerebral infarction. Also, since a lipid-rich plaque is observed in a human whose blood cholesterol level is not high and a lipid-rich plaque once formed is difficult to be removed, an agent capable of regressing such a lipid-rich plaque efficiently has been desired.
Before now, it is known that coumarin derivatives of a particular structure have lipid-rich plaque regressing activity and/or ACAT inhibitory activity, and are useful for preventing or treating coronary syndrome and the like (WO02/06264 and WO03/059900).